1. Technical Field
The present invention relates to an illumination a device and a projector.
2. Related Art
As one type of light source devices used for projectors, light source devices that irradiate a phosphor layer with laser light as excitation light to produce fluorescence at a wavelength different from the excitation light are proposed (e.g., see JP-A-2809-277516). A light source device disclosed in JP-A-2009-277516 has three fan-shaped segment areas on a circular transparent base. A red phosphor layer is provided in a first segment area, and red light is emitted from the first segment area. A green phosphor layer is provided in a second segment area, and green light is emitted from the second segment area. A diffusion layer is provided in a third segment area, and blue light as excitation light for the phosphor layers is emitted from the third segment area.
In the light source device disclosed in JP-A-2009-277516, the red light, the green light, and the blue light are emitted from the three segment areas in a time division manner. However, a light distribution is different between the fluorescence emitted from the phosphor layer and the diffused light emitted from the diffusion layer. That is, the red light (fluorescence) and the blue light (diffused light) have different light distributions, and the green light (fluorescence) and the blue light (diffused light) have different light distributions. Specifically, the light distribution of the diffused light is narrower than the light distribution of the fluorescence. As a result, color uneveness may occur due to the difference in light distribution.
In order to solve this problem, a method is considered in which a diffusion layer with a high diffusing power is used to expand the light distribution of the diffused light to thereby align the light distribution of the diffused light with the light distribution of the fluorescence. However, the diffusion layer with a high diffusing power has drawbacks such as much backscattering and difficulty in forming a diffusion layer with excellent characteristics. Therefore, the use of the diffusion layer with a high diffusing power gives rise to the problem that light use efficiency is reduced due to the drawbacks.